This invention pertains to the field of hand-powered tools, more particularly to hand-powered tools used to drive fasteners or bolts, and more particularly to hand-powered tools which employ wrist motion to turn the driving shank. The present invention is a wrist-motion rotary hand tool which by easy manipulation, the components may be shifted from a low-torque arrangement into a high-torque-applying relationship.
Wrist motion driving tools are well known in the art. Conventional hand drivers are designed with coaxial components. Hand powered tools of this nature do not provide sufficient torque to tighten or loosen fasteners, such as screws or bolts, which are wedged or nested in place.
To overcome the above deficiency, different types of hand driven tools have evolved. Such devices often implement a non-linear shank to create greater torque during operation. U.S. Pat. No. 4,974,477 to Anderson teaches a wrist motion hand tool with a S-curve shaped shaft having a mount to receive tool driving or drilling inserts. U.S. Pat. No. 2,712,765 to Knight discloses a wrist motion hand tool having a box end for receiving a socket-type adaptor for attaching screwdriver heads and the like. U.S. Pat. No. 2,277,961 to Detmers discloses a brace adaptable for receiving screw and nut drivers. U.S. Pat. No. 1,752,703 to Simson discloses a hand drill or screwdriver having a handle angled with respect to the shank to allow wrist motion to rotate the shank. U.S. Pat. No. 1,642,569 to Winslow, et al. discloses a hand tool having an angled set off handle, and either a screwdriver or mounting chuck in rotary engagement with the handle.
Although the more advanced hand drivers disclosed in these and other patents have increased torque capabilities compared to the conventional designs, these devices still have deficiencies. Specifically, the insert bit of these devices can easily slip off the fastener in situations that demand high torque. Accidental slippage may result in injury to the operator, and may also gall or strip the threads or otherwise deform the fastener. Accordingly, previous designs have proved to be unreliable in circumstances requiring high torque.